The max level is 30 before and after promotion. I believe in my run I promoted all my characters at 15 as part of the test. I don't think you ever need to level past 20 to get full unpromoted stats (besides the random stats it starts giving you past Level 20 so you probably should just promote at 20.)
Please note that Enemies that have Bolt used to have the old Bolt which was more like the original Bolt (except for Level 4) in terms of area and range, except it did 25 damage. The new Bolt is like how I had Bolt 4: A melee spell that hits the entire team, but with altered MP costs and damage. The Bolt 2 now should be doing 20 damage and can hit the entire team, but the Mage should require that it stands next to someone to cast it. This is untested, so do enjoy the enemies with Bolt 3 and Bolt 4, Especially the boss Colossus (Bolt 3 does 50 and Bolt 4 does 120. Bolt 4 used to deal 100, so I doubt anyone's surviving it now if they had the HP for it before
If it ends up being quite the problem, at least in a few Normal Battles, I can change their spells around, though the Cavern Mage will probably keep it to match the other two Mages with Blaze 2 and Freeze 2, while at the same time, he is technically the boss of that map.
At the Ch. 5 Cavern Battle, Domingo (if you're using him) should have learned Shield by this point which can be cast on himself or others. Arthur should know Void as well, though he can only cast it on himself. Yogurt might be the only one with Void 2 by this point who can affect a group. You should have picked up the Guardian Staff in the Chest in Waral, which also can be used with its Normal Attack option to cast Shield. There are many ways to protect from Magic for the late game, but perhaps not so much here, but do your best
Also note that the Shield spell protects from anything that can be used via the "Magic" menu. Normal Attacks which cast magic will NOT be blocked by Shield, and on the flip side, Physical Attacks used through the Magic Menu (Snipe, Charge, Crush, etc) will be blocked by Shield.
The original Chapel Battle (and Mine battle at the start of Chapter 3) had all the Skeletons knowing Slash 1. I removed some of these for the sake of your sanity (though it was still very possible before to do these battles as these changes happened AFTER my test run of my mod). Should I just give them their Slash 1 back?
Weeds were in the original game, just not used. Oddly enough, I assumed Weed was meant for Seaweed, since we kinda already had Land Golems. Not only that, Weeds naturally can walk on Water Panels in the original. The Ghouls here can be whatever you want them to be. Its the same one from the Abbey fight. I wanted to find a place to properly reuse them as regular enemies (as I made its stats and level to reflect a higher level mob, considering it was the Abbey Boss). Trying to get the most out of my Enemy/Name slots.
While I didn't use Lowe in my test, I did use Ken. At Level 18 Promoted (with a Promotion at Level 15), he had 101 HP, 7 MP, 78 ATK (w/ Valkyrie), 64 Def (w/ Shield Ring), and 55 Agi. The best Paladin is Mae which has a better stat average than any of the Paladins, but I did this because of who she is: The daughter of the great Varios, since she has his blood in her. Also, she takes great pride, so she gives it her best. The other Paladins tend to be above average in at least one stat, and a moderate secondary. Pelle has great Defense, Earnest has great Attack (but is very squishy). Vankar is pretty average but he has early growth which bolsters his stats to be more effective earlier on.